Color television system



March 31, 1959 N. w. PARKER COLOR TELEVISION SYSTEM Filed April 8. 1952 Fig. I

Convergence Vo/fa I Def/ecr/on Coils E lecfron Guns e m r M 7 CR 3 c P I m m m n ye mm MW 0 mm H6 V I far/c Convergence Vo/Ibge INVENTOR Norman W Parker A f A BY J shadow mask.

United States Patent M COLOR TELEVISION SYSTEM Norman W. Parker, Park Forest, 11]., assignor to Motorola, Inc., Chicago, 111., a corporation of Illi- 11015 Application April 8, 1952, Serial No. 281,178

14 Claims. (Cl. SIS-13) The present invention relates to color television receivers and more particularly to a system for converging the beams of a cathode ray tube of the type having a plurality of separately controlled electron beams containing different color information.

For providing color television, cathode ray tubes have been developed wherein a plurality of beams are used to produce different colors. In such tubes, it is necessary to converge the beams which originate at different positions so that the pictures of dilferent colors are in proper registry. One such tube is a direct view cathode ray picture tube having a multi-color phosphor surface comprising a plurality of separate and distinct phosphor dots, each dot emitting light of a selected one of two or more different primary colors. The different color phosphor dots are closely internested in symmetrical groups, each group being positioned behind an opening of a shadow mask, the shadow mask being positioned between the electron beam source and the phosphor surface. The shadow mask has a very large number of openings in order to provide sufficient picture detail. Each different color phosphor dot of the phosphor groups behind the mask is arranged to be scanned by a separate electron beam which is individually modulated with the color information for the particular color of phosphor dots.

The separate individually modulated electron beams in such a tube may originate from dilferent electron guns within the tube neck, with all of the beams being simultaneously deflected by common horizontal and vertical deflection systems to thereby scan the shadow mask. All of the separate electron beams, originated at different symmetrical positions within the neck of the tube, are also passed through a voltage responsive convergence lens to cause the beams to convergeand cross at a point within the opening of the shadow mask wherefrom they continue toward the respective color phosphor dot of the phosphor dot group behind the mask opening. It is apparent that the focal length for the convergence lens means must vary in accordance with the deflected position of the electron beams if the beams are to be accurately converged and crossed within the openings of the shadow mask as the electron beams are deflected to scan the It has been found that the convergence lens voltage should be dynamically varied in accordance with the horizontal and vertical deflection voltage variations. A substantially parabolic waveform for the dynamically varying convergence voltage, varying in synchronism with the horizontal deflection voltage, is satisfactory to produce the desired synchronized variation of convergence lens focal length.

It is a principal object of the present invention to provide a simplified circuit for converging swept beams in a dynamically varying manner in proper synchronism with the swept position thereof.

Another object of the invention is to provide a simple circuit for use with a color picture tube of the type including a plurality of beams originating from spaced sources producing a dynamically -varying convergence voltage with an approximately parabolic waveform during the active time interval during which the plurality of nant circuit tuned to the frequency of the horizontal deflection voltage and coupled to the deflection circuit in such manner as to convert a small portion of the horizontal deflection energy to a dynamically varying convergence voltage. The voltage of sinusoidal waveform developed in the resonant circuit may be phased to provide an approximate parabolic waveform during the time interval in which the horizontal deflection voltage is deflecting the electron beams to produce a horizontal line of a color television picture. The convergence voltage developed by the circuit of the invention may be readily mixed with a convergence voltage responsive to vertical deflection signals in order to produce complete dynamic convergence control.

Another feature of the invention is the provision of an inductance element in a resonant circuit for coupling to the horizontal deflection system in a manner to produce a dynamically varying convergence voltage, the inductance element being so designed as to provide a voltage step-up for the convergence voltage thus produced.

Yet another feature of the invention is the manner of coupling a resonant circuit to the horizontal deflection coils of a television receiver through a network of parallel connected high resistance elements in a manner to produce a dynamic convergence voltage without appreciably loading the horizontal deflection system.

Further objects, features, and the attending advantages of the invention will be apparent with reference to the following specification and drawings in which:

Fig. l is a diagrammatic view of one form of direct view color television picture tube for which the dynamic convergence voltage circuit of the invention may be used;

Fig. 2 is a schematic diagram of the circuit of the invention; and

Fig. 3 shows a family of curves representing various voltage waveform aspects of the invention.

In practicing the invention a voltage for converging the beams of a multi-gun color television tube, dynamically varying with the horizontal sweep, is produced by use of a resonant circuit. The resonant circuit is coupled to the horizontal deflection system through a network of high resistance elements connected in parallel with the horizontal deflection coils in a manner to minimize loading thereof. The resonant circuit includes an inductance and a capacitance and is tuned to the approximate frequency of the horizontal deflection voltage, i.e. 15,750 cycles per second. The inductance element may be an iron core coil having a winding effective to produce a voltage step-up ratio. In such manner a small amount of horizontal deflection energy is transformed into a sinusoidally varying voltage, the phase of which may be adjusted by the tuning of the resonant circuit, so that an effectively parabolic waveform is provided during the time that the electron beams are horizontally scanned to pro duce a horizontal line. The dynamic convergence voltage in the resonant circuit may be connected, together with a static convergence voltage and a vertically synchronized dynamic convergence voltage, to the convergence lens element of the picture tube to thereby obtain complete control of the focal length of the convergence lens for all deflected positions of the electron beam.

Referring to the drawings for a more detailed description of the invention, Fig. 1 diagrammatically shows one embodiment of a color television tube with which the circuit of the invention may be used. In order to simplify Patented Mar. 31, 1959 du'cing electron beams containing color information for blueand"redrespectively have been shown. It should be understood, however, thatiin at least one practical form of such television tube, three electron guns, symmetricallypositioned. within the'tube neck, are employed toproduce three differently modulated electronbeams" containing informationfor red,- blue 'andgreen primary colors. The electron beams 12 and 13 from the electron guns and 11 are passed through a convergence lens element 14 to cause said beams to converge andtcross at the .point 15 withinthe picture'tube.

A shadowmask 16 of metalor the like and having a large numberof small openings 17 'is positioned in a plane within the tube envelope 18 at a point intersectingthe point '15'at which the electron beams12 and 13. are converged. Theelectron beamsfl2 and"13'converging at thepoint '15 .pass through one of the-openings 17 of the shadow mask. 16 .and illuminate a red phosphor dot 19 and a blue phosphor dot 20 respectively. Thephosphor dotsi 19 and 20 are symmetrically grouped on the face of the picture tube behind the opening 17 of the shadow mask 16. The diagrammatic illustration of thetube as shown in Fig. 1 is intended to bea topplan viewshowing the electron beams 12 and 13 in two horizontal deflected positions. When theelectron beams 12 and13 arehorizonta'lly deflected to pass throughtheopening 21 of the shadow'mask 16it is apparent that the focallength of theconvergence lens 14 must be increased if the beams 12 and 13 are to converge and cross within the opening A static convergence voltage of about +9 kv., when applied to the convergence lens element 14, will produce a convergenceof the electron beams 12and 13 at the central. point 15 for one typical condition of operation of the color television picture tube 18. However, the con-" vergence voltage must be dynamically varied during the deflection of the electron beams in order to produce the dynamic variation of the convergence lens focal. length as referred to in the foregoing.

The electronbeams 12 and 13 are simultaneouslydeflected by horizontal and vertical deflection coils generallyshown at 22. In order to obtain the proper dynamic variation of the focal length of theconvergence lens 14 in accordance with the horizontally deflected positions of theelectron beams 12 and 13, a convergence voltage having a dynamically varying waveform of approximate parabolic shape is applied to the convergence electrode 14'during the time that the electron beams 12 and 13 are horizontally deflected from one side of the shadow mask 16 to the other to produce a horizontal line. It

should also be mentioned that the convergence voltage. for the lenselement 14 may be dynamically varied in f accordance with the vertical deflection of the electron beams12and 13, although the present invention is not directly concernedwith the manner of producingthe dynamically varying convergencevoltage that is syn chronized withvertical deflection. The desired approximate parabolic Waveform for the hynamic convergence voltage to be obtained by the circuit of the inventionv is shownby the curve 3a of Fig. 3 in the proper syn'-.

chronism with the horizontal trace time andthe retrace a controlof the amplitudeof dynamic convergence volt-" age to be'produced bythe circuit of the invention. J A resonant circuit comprising acoil 31 having a high permeability core andvariable condenser 32 is connected by'line33'to the connection between high-.resistance elea. merits-29 Tand30. In such. manner a smallpbrtion of the a horizontal deflection energy in the deflection coils 25 and 26 is applied to the resonant circuit including the" coil 31 and condenser 32. The variable condenser 32 is adjusted to resonate the circuit at the frequency of the horizontal deflection voltage, which is, for standard television practice, 15,750 cycles per second.

The horizontal deflection voltage across the deflection coils 25 and 26 has a modified square Waveform in order to produce the desired deflection current of sawtooth waveform in the deflection coils. The small portion of energy connected 'by line 33 to the resonant circuit 31 and 32, having the modified square wave voltage waveform is transformed by the resonant circuit 31 and 32 to a sinusoidally varying waveform. Such Waveform is shown by the curve -3b'of Fig. 3 together with the sawtooth waveform of current induced in the horizontal deflection coils. The phase of the sine wave voltage may be adjusted by tuning of the resonant circuit, as is well known, so that the waveform of the voltage during the horizontal trace time is approximately parabolic.

waveform and synchronism to be used as a dynamically varying convergence voltage for the convergence lens 14 of a multi-gun color television cathode ray tube.

In order to provide a voltage step-up for the sinusoidallyvarying signal in the resonant circuit including the coil 31 and condenser 32, the coil 31 may be provided with the voltage step-up winding 34 to be connected by the coupling condenser '35 to the convergence lens 14 of The static convergence voltage having a potential of about 9 kv. is connected through a high resistance 36 to be mixed with the dynamicallyvarying convergence voltage from the coil 34. If desired,"

a dynamic convergence voltage which is synchronized with the vertical deflection system of the television receiver, as diagrammatically shownat 37, may be coupled the cathode ray tube.

through the coupling condenser 38 to the'resistance 236 to thereby provide a complete control of the convergence lens focal length for all deflected positions of the electron beams.

Various modifications may be made within the spirit of the invention and the scope of the appended claims.

I claim:

1. In a television receiver which includes a cathoderay picture tube having means for developing at least one cathode-ray beam therein, deflection elements associated with said picture tube and responsive to a cyclic the convergence element including in combination, a

resonant network adapted to be tuned to the frequency-Z of the cyclic deflecting signal, means for coupling the deflectionelements to said resonant network to impress thereon'a cyclic voltage corresponding to the deflecting signal and thereby to cause said resonant network to de-' velop a substantially sinusoidally varyingdynamic convergence control signal, and means for applying the dynamic convergence control signal to the convergence control element.

2. In a color television receiver which includes a cathode-ray picture tube having means for developing a pluralityof cathode-ray beams therein, deflection coil means associated with the picture tube and connected to a deflecting signalsource to derive a cyclic deflectingsig nal for deflecting the beam, and a convergence control element associated with the tube, a circuitfor producing:

a dynamic convergence control signal for the convergence element including in combination, a resonant. network adapted to be tuned to the frequency of the deflccting signal, means for coupling the deflection coil means to said resonant network to impressthereonacyclic voltage corresponding to the-deflecting signal and thereby to Thus in eflect'the active portions of the sine wave as shown by the curve 3c of Fig. 3 is of the approximate correct cause said resonant network to develop a substantiallysinusoidally varying dynamic convergence control signal, and means for applying the dynamic convergence control signal to the convergence control element.

3. In a color television receiver which includes a cathode-ray picture tube having means for developing a plurality of cathode-ray beams therein, a pair of seriesconnected deflection coils associated with the picture tube and connected to a deflecting signal source to derive a cyclic deflecting signal for deflecting the beams, and a convergence control electrode associated with the tube; a circuit for producing a dynamic convergence control signal for the convergence control electrode including in combination, a resonant network adapted to be tuned to the frequency of the deflecting signal, a resistive network connected in parallel with the deflection coils and having an intermediate tap connected to said resonant network for impressing thereon a cyclic voltage corresponding to the deflecting signal thereby to cause said network to develop a substantially sinusoidally varying dynamic convergence control signal, and means for applying the dynamic convergence control signal to the convergence control electrode.

4. In a color television receiver which includes a cathode-ray picture tube having means for developing a plurality of cathode-ray beams therein, a pair of seriesconnected deflection coils associated with the picture tube and connected to a deflecting signal source to derive a cyclic deflecting signal for deflecting the beams, said deflection coils developing a cyclic voltage thereacross corresponding to the deflecting signal, and a convergence control electrode associated with the tube; a circuit for producing a dynamic convergence control signal for the convergence control electrode including in combination, a resonant network including an inductance coil shunted by a capacitor and adapted to be tuned to the frequency of the cyclic voltage, a resistive network connected in parallel with the deflection coils and having an intermediate tap connected to said resonant network for impressing the cyclic voltage across said network to cause said network to develop a substantially sinusoidally varying dynamic convergence control signal, and means including a voltage-step-up winding seriesconnected to said inductance coil in said resonant network for applying the dynamic convergence control signal to the convergence control electrode.

5. In a color television receiver which includes a cathode-ray picture tube having means for developing a plurality of cathode-ray beams therein, a pair of series connected deflection coils associated with the picture tube and connected to a deflecting signal source to derive a cyclic deflecting signal for deflecting the beams, said deflection coils developing a cyclic voltage thereacross corresponding to the deflecting signal, and a convergence control electrode associated with the tube; a circuit for producing a dynamic convergence control signal for the convergence control electrode including in combination, a resonant network having one side connected to a point of reference potential and including an inductance coil shunted by a capacitor, said resonant network adapted to be tuned to the frequency of the cyclic voltage, a fixed resistor and a variable resistor series-connected across the deflection coils and to said point of reference potential, the common junction of said resistors being connected to the other side of said resonant network for impressing the cyclic voltage across said resonant network to cause said network to develop a substantially sinusoidally varying dynamic convergence control signal, and means including a voltage step-up winding seriesconnected to said inductance coil in said resonant network for applying the dynamic convergence control signal to the convergence control electrode.

J6. In a television receiver which includes a cathodemy picture tube having means for developing at least one cathode-ray beam therein, deflection elements associated with said picture tube and responsive to a cyclic deflecting signal for deflecting the beam, and a convergence control element associated with the tube for producing a convergence effect on the beam; a circuit for producing a dynamic convergence control signal for the convergence element including in combination, resonant'network means adapted to be tuned to the frequency of the cyclic deflecting signal, means for impressing on said resonant network means a cyclic voltage corresponding to the cyclic deflecting signal to cause said resonant network means to develop a cyclic. dynamic convergence control signal, and means for applying the dynamic convergence control signal to the dynamic convergence control element.

7. In a television receiver which includes a cathode ray picture tube having means for developing a cathode ray beam therein and having horizontal deflection means associated therewith for producing a deflecting field varying cyclically at a predetermined frequency for deflecting the beam to various horizontal positions, an electron beam controlling lens system having a focal length which varies with the horizontal position of the beam including in combination, a resonant network tuned substantially to the predetermined frequency of the deflecting field, means for coupling the horizontal deflection means to said resonant network to impress thereon a cyclic voltage wave of the predetermined frequency thereby to cause said resonant network to develop a control wave at the predetermined frequency and of generally sinusoidal wave form, said control wave having a phase relation with respect to the deflection field such that said control wave includes portions of maximum amplitude occurring when the beam is substantially in a central deflected horizontal position, and means including said resonant network forming an electron beam controlling lens the focal length of which varies with the amplitude of said control wave.

8. In a television receiver which includes a cathode ray picture tube having means for developing a cathode ray beam therein and having horizontal deflection means associated therewith for producing a deflecting field varying cyclically at a predetermined frequency for deflecting the beam to various horizontal positions, a dynamic electron beam converging system for the electron beam of the cathode ray picture tube including in combination, a resonant network tuned substantially to the predetermined frequency of the deflecting field, means for coupling the horizontal deflection means to said resonant network to impress thereon a cyclic voltage wave of the predetermined frequency thereby to cause said resonant network to develop a control wave at the predetermined frequency and of generally sinusoidal wave form, said resonant network including adjustable tuning means for controlling the phase of said control wave, and convergence means including said resonant network forming an electron beam controlling lens the focal length of which varies with said control wave.

9. In a cathode ray tube image-reproducing system wherein electron beam energy is angularly deflected both horizontally and vertically relative to the longitudinal axis of the tube to scan a raster at a target electrode, means for eifecting said beam deflections with at least one beam deflection being under the control of a wave having a substantially sawtooth form, a dynamic electron beam controlling system comprising, field-producing means disposed adjacent to the undeflected path of said electron beam energy, and means to produce a wave varying as a sinusoidal function of said one beam deflection and having the same frequency as said one beam deflection for energizing said field-producing means.

10. In a television receiver which includes a cathoderay picture tube having means for developing at least one cathode-ray beam therein, deflection elements associated with said picture tube and responsive to a cyclic deflecting signal for deflecting the beam, and a convergence control element associated with the tube for producing a convergence efiect' on the beam; a circuit-{01 produclng adyn'amic convergence-control signal 'for the convergence-element including in combination, resonant thecycl-ic deflecting signal, passive coupling means 'for impressing on said resonant network means "a cyclic voltnetwork means'adapted to be tuned to the-frequency 'of agewave of modified-square wave formcorresponding to the cyclicdeflecting-signal to cause said resonant network means to developa cyclic dynamic convergence control signal, and means for I applying the dynamic con-. vergence control signal to the dynamic convergence con-- trol element;

11. In a television receiver which includes a cathode--' ray picture tube having means for developing at least one cathode-ray'beam therein, deflection elements-associated with said picture tube and responsive -to'a cyclic deflecting signal for-deflecting the beam, and a convergence-con trol element associated with the tubefor producing a'convergence effect on the beam; a circuit'for producing a dynamic convergence control signal forthe' convergence element including in combination, resonant network means adapted to be tuned to the frequency of-the-cyclic deflecting signal, passive-coupling means' connecting said resonant network means to said deflection elements-for impressing on said-resonant network means the cyclic deflecting signal to cause said resonant network meansto A develop a cyclic dynamic convergence control signal, and

means for applying the dynamic convergence control sig'- nal. to the dynamic convergence control element.

12; In a cathode ray tube image-reproducing -system the contro'l' of a wave having a substantially sawtooth" form with trace and retrace portions, a dynamic electron beam controlling system including, field-producing means disposed adjacent-to the undeflected'path'of said electronbeamcomponents, and resonant networkmeans coupled toithe meansfor effecting beam deflection -to produce-a control wave having the=same frequency as said onebeam' deflection' forenergizing said field-producing means, said control wave having 'portions ofsubstantially parabolic wave form which coincide in time with the trace portions of the sawtooth deflection Wave.

13. In a television receiver whichincludes a cathoderay picture'tube having means fordevelopinga cathode ray beam therein and having horizontal deflection means associated therewith for' producing a'deflecting field varying' cyclically at'a predeterminedfrequency for deflecting"- the 'beam to various horizontal positions,- an electron beam controlling lens system having a focal lengthwhich' varies with "the horizontal position of the beam including in combination; resonant network means 'tuned to provide resonant action at thepredetermined-frequencyof the deflecting field; means'for-coupling the horizontaldeflectio'n'rneans to said resonant network meanstoimpress thereon a cyclic voltage wave of'the predetermined fre' quency--thereby to cause said resonant network means to developa control wave, said control: wave having a phase relation with respect to thedeflection field such thatsaid" '-control' 'wave includes "portions of maximum amplitude occurring'whenthe'beam is substantially' in a-central 'hori zontal' 'position, said resonant networkmeans-including adjustable tuning means forcontrollingthe phase of said 1 control wave, andmeans including-said resonant networkmeans for'mingan electron beamcontrollinglens the 'focal length of which varies with the amplitude of said control 14. '-In-'a television receiver whichincludes-a cathoderay 'picture tube having means for developing cathode i'ay bearrr components thereinand having horizontal-dc-- fiec'tion 'means--associated'- therewith .for producing-a deflecting field-"varying cyclically at a predetermined fre-- quency for-deflecting the" beam components to varioushorizontal positions, a dynamic electron beam converging ray picture tube includingin combination, 'resonantnetwork means tuned to provide resonant-action at the pre-@ determined frequency ofthedeflectin-g field, means-for J coupling the horizontal deflection means to said resonant with: the: amplitude of said control wave.

Referencesjflitedin the file'of this patent UNITED STATES PATENTS 2,118,093 Zworykin et al Oct. 31,v 1939'v 2,220,303"; Tingley Nov; 5, 1940: 2,408,040 Busignies Sept. 24, 1946- 1 2,454;3 78 Forgue Nov. 23, 1948a 2,457,175 Parker Dec. 28, 1948: 2,581,487. Jennyr. Jan.,8,'-1952 2,601,153 Knight June-17, 1952. 2,623,195: Best- Dec. 23, 1952 2,664,521, Schlesinger Dec. 29, 1953, a 2,672,574. Evans- Man-16,1954, a 2,737,609 Kell-y etal. Mar. 6, 11956 FOREIGN iPATENTS 503,462, Belgium June 15, 1951. 866,065" 1 France Mar. 31, 1941:

OTHER REFERENCES Article -by- -Frienda-in; Proceedings of the; .-I.R.E.,'??,

October 1951; pp. 1249-1263.

system-for the electron beam components-of-thecathodenetwor-k meansto impressihereon' a cyclic voltage wave ofthe predeterminedfrequency, whereby said'resonant networkcdevelops a control waveat the predetermined I frequency and -having portionsof substantially parabolic wave 'formy said resonantanetwork means including ad- 1 justa-ble tuningmeansfor controlling the phase of'said controlwave,-andconvergence means includingsaid 1 resonant -network: means forming an electron beam controlling lenspositioned along-the undeflected'path ofthe beam :componentsand having'afocal length which varies? 

